The invention concerns a ring member of reinforced plastic construction for a wrapping machine, said ring member being rotatable and having a mainly ring-shaped structure.
The invention is associated with a wrapping machine whose wrapping unit comprises a rotatable wrapping ring member. The wrapping ring member has the shape of a circular ring and, usually supported by rollers, rotates in the wrapping machine either in a horizontal plane or in a vertical plane, while the object to be wrapped is wrapped by means of a plastic film band roll rotating with the ring member.
The wrapping ring member is usually made of a metallic material, but wrapping ring members of reinforced plastic construction are also used. A wrapping ring member of reinforced plastic construction is presented in patent EP 0 747 287 A1. However, a reinforced plastic structure has generally not proved to be strong enough to withstand the stresses caused by the roll of plastic film band rotating with the wrapping ring. It has been established that, especially as the rotational speed increases, the reinforced plastic structure is bent, causing problems. On the other hand, if the wrapping ring member of reinforced plastic is implemented as a very massive structure, then it will be difficult to manufacture, so this is economically not sensible.
The object of the present invention is to achieve a new type of wrapping ring member of reinforced plastic, which does not have the disadvantages, described above.
The wrapping ring member of the invention for a wrapping machine is characterized in
that the ring member of reinforced plastic construction for a wrapping machine comprises a box-shaped portion having a plurality of reinforcing fibre layers laminated in different directions upon a core part of cellular plastic or equivalent material,
that the box-shaped portion of the ring member is provided with a reinforcement laminated inside the reinforced plastic layers in the box-shaped portion, said reinforcement being preferably made of steel,
and that the reinforcement is a ring of the same form with the ring member or its length only equals part of the length of the ring member.
In cross-section, the box-shaped portion of the ring-shaped member may be e.g. of a rectangular, polygonal or circular form. Other forms different from these are also possible. The essential point is that the form and structure of the ring member are designed to achieve a light and strong ring that is well able to withstand the centrifugal forces generated by the rotating ring member and the plastic film feed apparatus moving together with it.
A preferred embodiment of the apparatus of the invention is characterized in that at least one of the reinforced plastic walls of the box-shaped portion of the ring member is inclined at an angle deviating form a vertical or horizontal plans.
A second preferred embodiment of the apparatus of the invention is characterized in that the reinforced plastic wall of the box-shaped portion of the ring member which is in engagement with a support roller and/or guide roller of the ring member is inclined at an angle of preferably 45xc2x0 relative to the vertical plane.
A third preferred embodiment of the apparatus of the invention is characterized in that the reinforced plastic box-shaped portion of the ring member comprises at least one flange for support and/or guide rollers, which Is made of the same reinforced plastic material.
A fourth preferred embodiment of the apparatus of the invention is characterized in that the flange of the ring member is preferably oriented in a direction inward from the box-shaped portion toward the centre of the ring member or in the opposite direction, outward from the ring member. Yet the flange may also be oriented in any other direction that gives the ring member advantageous strength properties. Thus, the flange may be oriented e.g. in an upward or downward slanting direction.
A fifth preferred embodiment of the apparatus of the invention is characterized in that the box-shaped portion of the ring member comprises two or more flanges, which may either be all oriented in the same direction, partially in different directions or they all may be oriented in different directions.
A sixth preferred embodiment of the apparatus of the invention is characterized in that the reinforcing fibres in the box-shaped portion and/or flanges of the ring member are preferably carbon fibres, the binding agent binding the reinforcing fibres is preferably epoxy resin, and that the core part inside the box-shaped portion is preferably made of foamed polyurethane plastic.
A seventh preferred embodiment of the apparatus of the invention is characterized in that it comprises at least one bolt going through the box-shaped portion of the ring member and through the core part of it, by means of which bolt the feed apparatus for a plastic film band roll can be connected to the ring member.
An eighth preferred embodiment of the apparatus of the invention is characterized in that it comprises at least one threaded sleeve or cup-like threaded part laminated inside the box-shaped portion of the ring member, to which threaded sleeve or part the feed apparatus of the plastic film band roll is connected with bolts.
A ninth preferred embodiment of the apparatus of the invention is characterized in that the reinforcement inside the ring member is provided with at least one threaded hole for the attachment of a feed apparatus for a plastic film band roll.
A tenth preferred embodiment of the apparatus of the invention is characterized in that it comprises one or more guide or support rollers connected either directly or via an adapter element to the box-shaped portion or flange of the ring member.
The invention also relates to a method for the manufacture of a ring member of reinforced plastic construction for a wrapping machine.
By prior-art manufacturing methods, it has not been possible to produce sufficiently strong ring members of reinforced plastic construction for a wrapping machine. Prior-art ring member structures are massive but still too flexible. The object of the present invention is to achieve a method that does not have the above-mentioned disadvantages.
The method of the Invention is characterized in
that the ring member of reinforced plastic construction for a wrapping machine is formed to a ring-like enclosure by laminating several reinforcing fibre layers in different directions upon a core part preferably made of cellular plastic or equivalent material,
and that inside the reinforced plastic layers in the box-shaped portion is laminated a reinforcement, which is a ring of the same form with the ring member or its length only equals part of the length of the ring member, and being preferably made of steel.
A preferred embodiment of the method of the invention is characterized in that the ring member of reinforced plastic construction is manufactured by
laminating the box-shaped portion upon the core part of cellular plastic or equivalent material by laminating several reinforcing fibre layers with varying fibre directions on top of each other, and
after that, pressing the core part and the box-shaped portion laminated upon it against each other.
A second preferred embodiment of the method of the invention is characterized in that the ring member of reinforced plastic construction is manufactured by pressing, after lamination of the reinforced plastic layers of the box-shaped portion, the reinforced plastic layers onto the core part by means of presses.
A third preferred embodiment of the method of the invention is characterized in that
a flange is formed in the box-shaped portion of reinforced plastic construction by laminating several reinforcing fibre layers with different fibre directions upon a core part of cellular plastic or equivalent material and bending the edges of the layers over each other to form a flange,
whereupon the reinforcing fibre layers of the box-shaped portion are pressed upon the core part and the edges of the reinforcing fibre layers forming the flange are pressed against each other.
A fourth preferred embodiment of the method of the invention is characterized in that the ring member of reinforced plastic construction is manufactured by making the box-shaped portion and/or flanges by laminating several layers of carbon fibres with epoxy resin on top of each other upon a core part of foamed polyurethane plastic.
A fifth preferred embodiment of the method of the invention is characterized in that the ring member of reinforced plastic construction is manufactured by
first laminating the box-shaped portion by laminating several reinforcing fibre layers with varying fibre directions on top of each other,
and after that supplying foaming cellular plastic or equivalent material into the space inside the box-shaped portion.